Walk-through rendering systems allow a graphics user to move through a synthetically modeled environment via computer graphics. In such a system a user can look at aspects of the environment that are of interest, and the user can interactively control both position and orientation within the model. Walk-through rendering systems are used for various purposes including previewing of buildings by architects prior to the actual construction of the buildings, and evaluating different design options by interior designers.
In the area of walk-through rendering systems, there are two basic systems used to render an image on the screen. The classic system is referred to as the polygon-based rendering system. The polygon-based rendering system is well known in the art and described in such textbooks as 3D Graphics Programming with QuickDraw 3D, by Apple Computer, Inc., Addison-Wesley Publishing Company, 1995.
The polygon-based rendering system describes the world in polygons, where each identifiable image is created from a combination of polygons. One constraint of the polygon-based rendering system used for walk-through systems is the amount of time available for computing an image. The image must respond interactively to the user's input, which can cause the interactive image to be a relatively crude representation of the scene.
The second basic type of rendering system is an image-based rendering system. An example of a system utilizing the image-based rendering approach is QuickTime VR, manufactured by Apple Computer, Inc. The image-based rendering system is also well known in the art and is taught by publications such as U.S. Pat. No. 5,396,583 issued Mar. 7, 1995 to Chen et al., and U.S. Pat. No. 5,446,833, issued Aug. 29, 1995 to Miller, et al., both of which are assigned to the assignee of the present invention. The image-based rendering systems describe the world as a series of images. It can be thought of as a series of still photos surrounding the viewer which can generate every view from a particular viewpoint.
In a walk-through rendering system using image-based rendering, the viewer may look around, but cannot change her location. The images projected by the image-based rendering system display a view of a scene from a single location. If the viewer's location shifts, then a new image from a new viewpoint must be generated. A walk-through rendering system utilizing image-based rendering may constrain either or both the user's location and their viewing direction at run-time. However, the images generated by the conventional image-based rendering systems are typically of higher quality than those generated by the conventional polygon-based rendering systems on a given computing platform. Because image-based rendering systems resample source images of a scene, rather than relying on a polygonal representation of that scene, the imagery can be as complex as the source image representation allows without affecting the computational cost.
What is needed therefore is a system which overcomes the disadvantages described above with respect to known rendering systems. The present invention addresses such a need.